a. Field of the Invention
This invention relates to a method for oxidizing cyclohexane with nitrogendioxide, and followed by oxidizing the intermediate product i.e. said precursor with liquid nitrogendioxide N.sub.2 O.sub.4 for the purpose of producing adipic acid.
B. Description of the Prior Art
A number of prior arts of producing adipic acid have been known. In the industrial scale, adipic acid has been produced by a method by which acrylnitrile is dimerized by electrochemical hydrogenation to form dinitrile, and followed by hydrolysis of it, and also by the alternative method by which hydrogenation is effected to dimerize acrylnitrile in dimethyl sulfoxide by the use of sodium amalgam.
In the large scale production, however, adipic acid has been principally produced by oxidizing cyclohexane.
Hereinafter, mainly, the methods of producing adipic acid directly from cyclohexane are mentioned. 1. Chemical Technology 1974(9) disclosed on page 555 - 559 that adipic acid was produced by oxidizing cyclohexane by molecular oxygen under a pressure, at a temperature about 80.degree. - 90.degree. C in the presence of catalyst and initiator in acetic acid. The selectivity rate of adipic acid was 72 - 74%, and conversion rate of cyclohexane was 82 - 88%. 2. Ullmann Encyclopaedia Der Technische Chemie Bd. 3 (1953) disclosed on page 95 that cyclohexane was oxidized by nitric acid under a pressure of 2 - 15 atm at a temperature of 90.degree. - 120.degree. C in about 12 hours to produce adipic acid in an yield about 34% with nitrocyclohexane in an yield about 16%.
Furthermore, the following methods are known. 3. Japanese Patent Publication No. 3812/1964 disclosed that cyclohexane reacted with nitrogendioxide at a temperature of 30.degree. - 70.degree. C in the presence of catalyst in 120 hours to produce adipic acid in an yield about 30% with nitrocyclohexane in an yield about 5%. 4. Roberto Lee, et al disclosed on page 411 - 420 Industrial and Engineering Chemistry Process Design and Development Vol 4, No. 4 1965 that cyclohexane reacted with nitrogendioxide in vapor phase to investigate variables including temperature, residence time, molar ratio of cyclohexane to nitrogendioxide and several different reactors. Nitrocyclohexane was obtained in an yield about 50% with other product such as adipic acid, cyclohexylnitrite, cyclohexylnitrate, cyclohexanone and cyclohexanol. 5. William F. Hoot et al disclosed on page 783 Industrial and Engineering Chemistry Vol. 47, No. 4 1955 nitrogendioxide was dissolved in cyclohexane and the mixture was allowed to react at a temperature of 50.degree. - 90.degree. C. Adipic acid was obtained at 50.degree. C in an yield of 98% in 43 hours, but in an yield of 5% in 2 hours. 6. A. Toptschien et al disclosed on page 1367 - 1368 B. 67 (1934) that cyclohexane reacted with nitrogendioxide under irradiation of ultraviolet ray in the presence of carbondioxide at temperature of 30.degree. and 80.degree. C in about one hour to produce nitrocyclohexane in an yield about 30% and 25% with no formation of adipic acid. 7. Japanese Patent Publication No. 24094/1969 disclosed that cyclohexane reacted with nitrogendioxide under irradiation of ultraviolet ray at a temperature of 25.degree. C in about 3 hours to produce adipic acid in a selectivity rate about 86% with nitrocyclohexane in selectivity rate about 8%. The conversion rate, however, of cyclohexane was about 10% so that the yield of adipic acid was low. 8. Japanese Patent Application No. 148908/1974 disclosed that cyclohexane reacted with nitrogendioxide under irradiation of ultraviolet ray or visible ray at a room temperature in the presence of oxygen to produce cyclohexanone, cyclohexanol and cyclohexylnitrite. However, adipic acid was not formed. 9. A. I. Titov et al disclosed on pages 241 and 242 J. Gem. Chem. USSR 23 (1953) that 350 ml cyclohexane reacted with 20g nitrogendioxide dissolved in 50 ml hydrocarbon at a temperature of 60.degree. C in 16 hours by introducing 3 l oxygen and 5.1g adipic acid and 6.7g nitrocyclohexane were obtained, and that 0.5g cyclohexane reacted with 1.4g nitrogendioxide at a temperature of 100.degree. C in 3 hours to obtain 0.21g adipic acid with 0.04g nitrocyclohexane. 10. A. I. Titov disclosed on page 567 Tetrahedron 1963 Vol. 19 the free radical mechanism of nitration. However, there was no disclosure of photochemical oxidation of cyclohexane with nitrogendioxide in the presence of oxygen. 11. In Chemischen Information Dienst 22 Juli 1975, there is a description "Beim Einleiten von Ozonisierten Sauerstoff und Stickoxid bzw Stickstoffdioxid in Cyclohexan." In this report, the formation of adipic acid was found, but this reaction was not photochemical reaction.